Coke is produced by heating pulverized coal in an air free environment for a period of time. Typically, coke is produced in a coke oven battery which includes a plurality of side-by-side coking chambers which are separated from each other by heating walls. The side of the coke oven battery where the coke is discharged is called the coke side, and the other side is called the pusher side, the heating walls and the coking chambers extending from one side to the other. In a typical installation the battery may include 40 to 100 or more side-by side coking chambers, each chamber being from 3 to 6 meters high, typically 14 meters long, and approximately 1/2 meter wide. There is a slight taper to the width of each chamber so that coal which has been coked within the chamber may be pushed out of the chamber, the width of a chamber at the pusher side being typically 3 inches less than the width at the coke side. Each heating wall is typically built up from a number of horizontally extending courses of silica bricks, the bricks being assembled to define vertically extending flues within the heating walls, which flues cycle between heating and drafting conditions. There may be six bricks or more in each course for each flue. Thus, in a heating wall having twenty-six courses and twenty-eight flues there may be over 4,300 bricks, each brick being location specific.
The coking chamber is normally maintained at a temperature of from 2100 degrees to 2500 degrees Fahrenheit. The coal to be coked is placed (or charged) within the coking chamber through charging holes at the top of each coking chamber. During charging and the following coking period, which may be 24 hours long, coke oven doors close off the ends of the coking chamber. While the coking process takes place, gases are driven from the coal, which gases include hydrocarbons such as methane, hydrogen, carbon dioxide, and many others. These gases are typically collected for processing into various by-product chemicals and eventual use as a fuel. The gases driven from the coal initially pass through standpipes which extend upwardly from the roof of the coke oven battery, the gases then being received by a collecting main.
At the completion of a coking cycle, the coke oven doors are removed from both ends of the coking chamber and the coked coal is pushed from the coking chamber by a pusher which is forced entirely through the coking chamber, the coke passing through a coke guide into a quenching car. When the doors are opened, the pressure within the coking chamber will be immediately released and condensed gases or liquor from the collecting main may reverse flow through the standpipe onto the silica bricks causing their surfaces to spall. In addition, the cold air which rushes in after the completion of the coking operation may also adversely affect the surfaces of the silica bricks, as silica bricks has poor resistance to thermal shock.
In any event, after a number of coking cycles over a period of years the surfaces of the silica bricks, particularly at the end of the heating wall adjacent the standpipes, become damaged.
U.S. Pat. No. 2,476,305 discloses that a heating wall in a coke oven may be repaired by replacing individual bricks. A more recent U.S. Pat. No. 4,452,749 also discloses a repair wherein individual bricks are replaced, the bricks in this case being molded from a castable refractory mix which, after molding, expands to only a negligible degree during heating up from ambient to the operating temperature of the coking oven. However, U.S. Pat. No. 4,452,749 only discloses the use of bricks having essentially the same size as the bricks which they are replacing as it was not known how to cast large refractory shapes until the time of the present invention.
It has also been proposed in U.S. Pat. No. 4,364,798 to rebuild a heating wall by removing the damaged brickwork, to install forms which will disintegrate when heated, and to then rebuild the removed brick by building up a unitary structure by using a gunning material of the type well known for sealing cracks in coke ovens and for relining furnaces. However, the gunning material proposed has the expansion and contraction properties of the silica brick which it replaces, and it may buckle during expansion and crack during cooling. Accordingly this design has not received any commercial success. Finally, it is conventional practice to simply spray a slurry on the face of the bricks by a gunning application of a refractory gunning material as discussed in Cols. 1 and 2 of U.S. Pat. No. 4,364,798.
Today the only practical method of performing a repair for long-term future service is to knock down the portion of the wall which is to be repaired and to rebuild it with silica bricks or with shapes cast to the shape and form of silica brick as done in U.S. Pat. No. 4,452,749. This process is very labor intensive. In view of the high labor costs involved, as well as the relatively high cost of the silica bricks required, this process is also a very expensive proposition.